Homework Help:
Ring -singularity (Determinant of the Kerr metric)

My problem is as follows:
"Calculate the determinant of the Kerr metric. Locate the plac where it is infinite. (In fact, this gives the "ring"-singularity och the Kerr black hole, which is the only one)

and I talked to my prefessor and he told me that the answer should be the equation of a ring (x2+y2 = constant) in spherical coordinates, I have all this in Boyer-Lindquist coordinates I believe, and according to wikipedia